Vitamin D3 is a vitamin involved in various functions including metabolism and homeostasis maintenance of calcium and phosphorus, and bone formation, and is produced from cholesterol in the human body. However, because the quantity of vitamin D3 produced in the body is smaller than the required quantities, vitamin D3 needs to be ingested through food, drug products, or supplements.
Vitamin D3 contained in drug products and supplements is produced mainly through ultraviolet irradiation of 7DHC produced by chemical transformation from cholesterol obtained from wool. However, use of animal-derived materials as source materials of drug products and supplements tends to be avoided due to the concerns of BSE and zoonosis, and there is a need for vitamin D3 derived from non-animal. Vitamin D3 derived from non-animals can be produced through ultraviolet irradiation of 7DHC derived from non-animal.
Generally, sterols produced by microorganisms are ergosterols. However, some members of oomycetes and Labyrinthulea microorganisms are known to produce cholesterol (Non-Patent Documents 1 to 3). 7DHC is converted into cholesterol by the action of 7DHC reductase. Therefore, it is theoretically possible to produce non-animal-derived 7DHC by reducing or eliminating the 7DHC reducing activity in these microorganisms and using the same for fermentative production or the like.
However, there are reports that significant amount of 7DHC is not accumulated in humans, mice, and budding yeasts. Specifically, there are reports that in humans and mice, 7DHC production involving a loss of 7DHC reducing activity causes decomposition of HMG-CoA reductase that catalyzes the rate-limiting step of cholesterol synthesis, and significantly reduces 7DHC accumulation (Non-Patent Documents 4 to 6). As to the budding yeasts, there is a report that 7DHC production involving introduction of 7DHC reductase significantly reduces 7DHC accumulation (Non-Patent Document 7).
Further, there are reports that a loss of 7DHC reducing activity causes Smith-Lemli-Opitz syndrome in humans (Non-Patent Document 8), and expression of a dwarf phenotype in plants (Non-Patent Document 9). That is, a reduction or a loss of 7DHC reducing activity was believed to have adverse effect on the growth of the host organism.